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A Web music store offers two versions of a popular song. The size of the standard version is 2.7 megabytes (MB).
The size of the high-quality version is 4.5 MB. Yesterday, there were 800 downloads of the song, for a total download size
of 2700 MB. How many downloads of the high-quality version were there?
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Let x = # of 2.7 MB,
y = # of 4.5 MB.
Then
x + y = 800, 1)
2.7x + 4.5y = 2700. (2)
Solve this system, and you will get the answer.
You can use the substitution method.